A number of factors have contributed to the growing problem of air contamination in commercial, industrial, and residential buildings. For energy conservation, new buildings are being built to be very tight, that is, to minimize infiltration of outside air into the building, and minimize the release of air from the building to the outside except as controlled by the building heating, ventilating, and air conditioning (HVAC) system. Additionally, for energy conservation reasons, building owners often operate the HVAC systems in a manner that will minimize the induction of fresh air in very hot and very cold weather. Meanwhile, buildings house an increasing amount of equipment, furniture, and building materials, as well as chemicals used to clean and maintain the building and its contents, which contaminate the air within the building. Insufficient replacement of stale air with fresh air, combined with the release of contaminants into the building air, results in what is sometimes called the "tight building syndrome". The air in buildings with "tight building syndrome" has been found to contain, among other substances, hydrocarbons, both methane and nonmethane, formaldehydes, aldehydes, acrolein, nitrous oxide, carbon monoxide, hydrogen sulfide, ammonia, and hydrogen cyanide. The air frequently contains, as well, a high level of particulates, e.g., mold spores, pollen, and dust, which serve as vehicles to carry microbiological contaminants, as the particulate filters commonly used in the HVAC systems are not very effective, and are often not properly maintained.
NIOSH (National Institute for Occupational Health and Safety) and investigations have been undertaken relative to indoor air quality. Investigations have been conducted in private and government sector office buildings, as well as in schools, colleges, and health care facilities. The symptoms and health complaints reported by the workers and occupants of the buildings have been diverse, and not specific to any particular medical diagnosis or readily associated with a causative agent. A typical spectrum of symptoms has included headaches, varying degrees of itching and burning eyes, irritation of the skin, including rashes, sinus problems, dry and irritated throats, and other respiratory irritations. The work place environment has been implicated, by virtue of the fact that symptoms normally disappear on weekends, when people are away from the office. At times these symptoms have been severe enough to result in missed work, lost time, reassignment, and even termination. This has caused increased anxiety among workers, and often times has made the investigation in these areas difficult and frustrating.
Although some of these episodes may be multi-factorial, most of the studies have been classified by the primary types of problems found. In recently reported investigations, inadequate ventilation was determined to be the cause in 52% of the investigative cases. Contamination inside the building resulted in 17%. Contamination from outside the buildings was indicated by 11%. Microbiological contamination was attributed to approximately 5% of the problems in these studies. 3% of the cases were attributed to fabrics, wall treatments, formaldehyde emissions from wall treatments, hangings, carpets, materials, fiber materials, polyester, fabrics, etc. Roughly 12% of the problems of the investigation were undetermined.